This invention relates to surgical instruments and, more particularly, relates to rotary cutting scissors used in removing soft tissue during surgery, such as arthroscopy.
In arthroscopic surgery, torn soft tissue in the knee is cut away to allow the knee to mend. Often, during athletic events, a participant will twist his knee in an awkward position such that he tears soft meniscus tissue within it. In order to repair the knee, it is sometimes necessary for a surgeon to remove the jagged portion of the tear and then go back and round the remaining marginal edge of the previously torn section. Otherwise, the tear will continue to rip and cause further damage. If the tear is removed, the damage is halted and the remaining tissue in the area of the tear is able to rejuvenate; the rounded edge of the cut tissue grows "outwardly" and knits with adjacent, undamaged tissue.
Recently, tiny, hand-held rotary cutting scissors have been introduced to enable a surgeon to more easily and surely cut away the toughest and most resistant cartilage and tissue. These prior devices, such as the ACUFEX.TM. rotary cutting scissors, manufactured by Acufex Microsurgical, Inc., consist of a rotary scissor assembly mounted at the end of a tiny shaft assembly so as to enable the surgeon to reach extreme posterior and anterior portions of the knee joint to increase cutting accuracy.
The ACUFEX.TM. scissor assembly consists of a pair of angularly offset scissor blades that can be serrated. One of the blades is fixedly mounted on an end of a stationary outer tube of the aforementioned shaft assembly. The other is fixedly mounted on an adjacent end of a concentric inner rod which is telescopically located within the outer tube and mounted for rotation therein by a cylindrical handle that supports the opposite end of the rod in a cantilevered fashion. The handle is parallel to both the inner rod and outer tube and includes a spring-loaded, thumb-squeezed plunger for rotatably driving the inner rod. By pushing down on the plunger with his thumb, the surgeon activates a "rack-and-pinion" gearing to rotate the inner rod, which in turn causes the scissor blade attached to it to rotate through a surface of revolution adjacent the fixedly mounted, stationary scissor blade. This produces a cutting surface between the mating scissor surfaces and enables the surgeon to cut away the damaged tissue.
While the ACUFEX.TM. device is useful, a major problem exists with it. Due to the drive mechanism being situated in a cylinder and its being actuated by a thumb-squeezing movement, the depth of the cut performed with this device is hard to control. The natural inclination of the user of this device is to tip or tilt the scissor end downwardly each time the the thumb is pushed down to actuate the device's plunger. Therefore, a surgeon has to consciously think about this problem and apply an awkward counter pressure to the bottom of the cylindrical handle which causes discomfort and subsequent fatigue.
While such fatigue may not matter if a doctor performs only one operation in a day since the doctor's hand has time to recuperate, it is a genuine concern when the doctor is in the midst of his third or fourth operation of the day, especially for the patient. The doctor's cutting accuracy may be decreased due to this fatigue.
Accordingly, it is the primary object of the present invention to provide an improved rotary cutting scissors for surgery in which the undesirable characteristics of the prior art are overcome.
It is a more specific object to provide a rotary cutting scissors with a new handle configuration and drive mechanism that does away with the problem of thumb fatigue found in the prior art.
It is another object to provide an improved rotary cutting tool that allows the user to more easily control the depth of his cut with the device.
It is a further object to provide an improved rotary cutting scissors that does not jam as easily as the prior art. In the prior art, there is a problem of separating the scissor edges when they become wedged together during the cutting of an extremely tough piece of tissue.
It is yet another object to provide an improved rotary cutting scissors in which the operating surgeon is able to keep the tip steady during the cutting in a precise perpendicular angle to the line of cut.
It is still another object to provide an improved rotary cutting scissors that is simple and economical in design, yet sturdy and effective to use.